Molded thermoplastic arch shape cross section corrugated chambers are now well-known for different applications, including receiving wastewater and stormwater. The description here focuses on a chamber for the wastewater function. The chambers are typically connected end to end to form a chamber string within a trench beneath the surface of the earth, which is then backfilled with soil, crushed stone, or other medium. Wastewater flowing into the chambers exits the open bottom and passes through the perforated side walls into the surrounding water permeable medium. A string of such chambers is preferably installed in a straight line and with a very small down-slope, if any, from the inlet end to the other. A typical chamber of such type is shown in U.S. Pat. No. 5,336,017 to Nichols. Such early kind of chambers had only a small ability to rotate at the joint, of the order of 3 degrees plus or minus; and, that was accomplished by negating, or making inferior, the otherwise positive straight-fit joint. See U.S. Pat. No. 5,588,778 of Nichols et al.
However, sometimes the land contour or subsurface obstructions prevent the string from running in a straight line. Thus, in an approach used in recent years, chambers have joints which enable a chamber to be angled at a desired horizontal plane angle relative to an adjoining chamber, at the time of installation. Such chamber joints are in the trade said to permit rotation or swiveling, although once installed, the selection of angle between chambers is not subsequently changed, owing to the backfill. Commonly owned co-pending patent application Ser. No. 10/442,810 of Burnes et al., describes both a separate coupling for use with chambers, and chambers having integral rotation means. Quick 4™ leaching chambers sold commercially by Infiltrator Systems, Inc. of Old Saybrook, Connecticut have features like the chamber shown in the patent application. See also U.S. Pat. No. 6,592,293 to Hedstrom et al. Generally, in the aforementioned art, rotation of one chamber relative to the other is enabled by a surface of revolution at one chamber end, called the dome end here, which acts as a male pivot when overlapped by the opposing end of a like chamber.
When the aforementioned type of chamber is installed end-to-end, with the intent that the row of chambers runs in a straight line, the rotational adjustability of the joint is not wanted. If a string of chambers is constructed so it lies in a too-wide trench or open pit, then some guide is needed to help the installer runs along a straight line. Accomplishing that can be important when the distance between adjacent strings or rows of chambers is regulated and when the minimum inter-row spacing is desired. An installer may place guide strings, shine laser beams, or use other guide aids. That can slow the installer down and the result can be uneven, depending on the installer's ability and care. Thus, there is a need for a chamber joint which permits positive straight line connection when that is desired, and rotation or off-angle installation when that is desired.